Fluid pressure actuated piezoelectric generator



Nov. 21, 1967 c. M. BENSON 3,354,327

FLUID PRESSURE ACTUATED PIEZQELECTRIC GENERATOR Filed Aug. 9, 1965 3 Sheets-Sheet l f v L l-HsH v 78 7O I FLLUD GENERATOR BMTOR TO H 74 SPARK HKvH 72 L S VOLTAGE \LL 2 OF EN \NTERNAL 4 coMaumoN l:

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FLUID PRESSURE ACTUATED PIEZOELECTRIC GENERATOR Filed Aug. 9, 1965 .3 Sheets-Sheet 5 FR" 196 I To SPARK PLUG GAE/V00 M. BENSON BY lame A WORN United States Patent 3,354,327 FLUID PRESSURE ACTUATED PIEZOELECTRIC GENERATOR Glendon M. Benson, Danville, Calif., assignor to Physics International Company, San Leandro, Calif., a corporation of California Filed Aug. 9, 1965, Ser. No. 478,223 16 Claims. (Cl. 3108.7)

This invention relates to high voltage generators, and more particularly to improvements in spark generators.

Ceramic materials have been developed which have piezoelectric properties. It has been found that these ceramics can generate Voltages sufliciently high so that they can be directly connected to devices, such as to spark plugs, for an internal combustion engine. However, one of the reasons why this has not been done is that the mechanism for applying the required pressures over the required short interval with the required repetition for use in an internal combustion machine has proven to be difficult to construct as well as expensive.

An object of this invention is to provide a novel and useful piezoelectric ceramic high voltage generator.

Yet another object of the present invention is the provision of a relatively simple piezoelectric high voltage generator.

Still another object of the present invention is the provision of a piezoelectric spark generator apparatus which is operable in conjunction with an internal combustion engine to provide the required spark voltages therefor.

These and other objects of the present invention are achieved in apparatus wherein a piezoelectric ceramic cylinder is driven in response to fluid pressures to provide the required voltages. The apparatus in the embodiment includes an accumulator for pressurized fluid with a valving mechanism such that the fluid, when a spark is required, is permitted to be applied to the piezoelectric ceramic device. The fluid pressure is then relieved. Fluid is then accumulated in the pressurized fluid accumulator for use when the next spark is required.

In another embodiment, a cam actuated piston applies pressure to a fluid which actuates a pressure plunger or second piston, which in turn applies pressure to a piezoelectric cylinder. After a predetermined pressure has been applied, the pressure is released and the voltage generated thereby by the piezoelectric device is applied to the spark plug device requiring it.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection With the accompanying drawings, in which:

FIGURE 1 is a schematic diagram of an embodiment of this invention;

FIGURE 2 is a cross-sectional view of an embodiment of this invention;

FIGURE 3 is a cross-sectional view along the lines 33 of FIGURE 2 illustrating the appearance of the embodiment of this invention when the pump is made integral therewith;

FIGURE 4 is a cross-sectional view along the lines 44 of FIGURE 3 illustrating a detail of the pump;

FIGURE 5 is a schematic view of a circular arrangement for a high voltage generator in accordance with this invention;

FIGURE 6 is a cross-sectional view along the lines 6-6 of the voltage generator shown in FIGURE 5;

FIGURE 7 is a cross-sectional view of another embodiment of the invention; and

FIGURE 8 is a cross-sectional view of an embodiment of the invention which does not use a rotating shaft as a valve means.

Referring now to FIGURE 1, there may be seen a schematic drawing of an embodiment of the invention. A high voltage generator 10, in accordance with this invention, which is to be used with an internal combustion engine 12, has a valve driven by the motor 12 through a shaft 14. The motor 12 also drives a fluid pump 16. The fluid pump applies fluid to the generator at a high pressure and the fluid is returned thereto at a low pressure. Where a single generator is employed for an engine, a distributor 18' is employed to distribute the voltage to the various spark plugs of the motor 12. In case a generator is employed for each spark plug in the motor, the distributor may be eliminated.

FIGURE 2 is a cross-sectional view of an embodiment of the invention. The structure of the invention is symmetrical about the center. It includes a solid body 20 having a fluid accumulator portion 24A which is substantially cylindrical in shape and a back portion 24B having the shape of a truncated column.

A piston 26 having the usual sealing ring 28 at the edges thereof to provide a movable seal with the walls of the cavity 24 is urged into the pressure fluid accumulating end 24A of the cavity 24 by means of a spring 28. The spring is mounted within the cavity portion 24B to push against the piston 26. A vent tube 30 permits air to escape from the portion of the cavity 243. Hydraulic fluid under pressure from the pump 16 is pumper through the tube 32 into the cavity portion 24A. A passageway 34 leads from the bottom of the cavity portion 24A, which is opposite the piston 26, to a valving means. This valving means consists of a rotary shaft 36 having a first and second passageway respectively 38, 40 therethrough. These passageways, as may be seen in FIGURE 3, are in side-by-side relation and make different angles with the axis of the shaft 36. The rotary shaft 36 is driven by the motor so that it will have one position wherein the passageway 34 and the passageway 38 are lined with another passageway 42 which is on the opposite side of the shaft 36. The shaft continues to rotate until the passageway 40 can align itself between another passageway 43, as may be seen in FIGURE 3, and a relief passageway 44.

The cavity 22 contains two piezoelectric ceramic cylinders respectively 46, 48 which are electrically axially poled. These cylinders are aligned with one another, such that their poling directions are toward the center electrode. One end of one of the cylinders is attached to the apex end of the cavity 22. The two cylinders are separated by a suitable electrode 5t), which can comprise plating on the abutting ends of the cylinders. The other end of the cylinder 48 is attached to a piston 52. The piston has a liquid seal 54 mounted at its edges so that no hydraulic fluid can pass around and behind the piston 52. An air vent 56 is provided for the space behind the piston 52. An electrical lead 58 is connected to the electrode 50 and is insulatingly brought through the walls of the body 20 and external to the cavity 22. The opposite ends of the piezoelectric ceramic cylinders 46, 48 are grounded to the body 20. Thus, the high voltage required is taken from between the lead 58 and the body 20.

In operation, as the shaft 36 rotates, pressurized fluid is pumped through the passage 32 into the portion 24A of the cavity 24 which is in front of the piston 26. The piston is pushed back upon the spring 28, thus accumulating pressurized fluid in the portion of the chamber 24A in front of the piston 26. When the shaft 36 is turned to align the passage 38 with the passages 34, 42, there is a sudden application of pressurized fluid to the base of the piston 52 causing it to exert a high compressive force upon the piezoelectric ceramic cylinders 46, 48. The result is the sudden generation of a high voltage which is applied, via the lead 58 and a ground connection, through the body 20, to a spark plug. As a result, the spark plug will spark whereby the voltage across the piezoelectric cylinders is discharged.

As the shaft 36 continues to turn, it aligns the passageway 40 with the passageways 43 and 44. This causes the strain which is placed upon the piezoelectric cylinders to be relieved since an exit passageway is provided for the fluid which was applied to' the piston 52. This fluid is evacuated. Meanwhile there is a build up of pressurized fluid in the chamber 24A against the time when the shaft 36 aligns passageway 38 with passageways 34 and 42.

The purpose of the pressure accumulator in the embodiment of the invention is to arrest pressure surges in the hydraulic fluid supply. Also, there is provided a short coupling distance for the hydraulic fluid supply which provides direct application of pressure from the source of the fluid at high pressure to the location at which it is used. The embodiment of the invention shown is simple to construct and maintain. It can be operated as rapidly as is required and provides consistent outputs.

A preferred arrangement for the embodiment of the invention is one wherein the pump is made integral with the spark generator itself. An arrangement for doing this is shown in FIGURE 3, which is a cross-sectional view along the lines 33 of FIGURE 2. It should be borne in mind here that the structure shown in FIGURE 3 is identical with that shown in FIGURE 2, except for the addition therein of the pump structure 60. Considering FIGURE 4 also, which is a cross-sectional view of FIG-. UR E 3 taken along the lines 44, the pump structure is seen as an extension of the shaft 36 into a pump housing portion 62 which shaft extension carries vanes 64. As the shaft rotates these vanes'within the pump cavity 66 in the pump housing 62 produce the necessary pressure build up of the hydraulic fluid which is fed thereto from the passageway 44. This fluid is pumped into the chamber portion 24A through a passageway (not shown).

While the embodiment of the invention has been described as capable of providing a succession of voltages for operating all of the spark plugs of an engine, it will be understood by those skilled in the art that it is preferred to either provide one of these generators for every spark plug employed in the engine, or one of these generators for several of the spark plugs in the engine. These arrangements may be made with a plurality of the embodiment shown in FIGURE 2 or FIGURE 3 aligned along a single rotary shaft 36 to be controlled by the passages which are spaced along said shaft, as shown in FIGURE 3, or may have an arrangement wherein the voltage generators are circularly distributed about a rotating shaft.

FIGURE is a schematic view of a circular arrangement of the piezoelectric voltage generator and FIGURE 6 is a cross-sectional view along the lines 66 of FIG- URE 5. The high voltage generator 70 has a rotatable shaft valve arrangement 72 similar to the type already described. This is driven from the engine 74. A fluid pump 76 is also required which is driven from the engine 74. The fluid pump provides hydraulic fluid to the high voltage generator which will contain a pressurized fluid accumulator of the type already described. The high voltage generator return-s the fluid back to the fluid pump 76. The output of the high voltage generator may be applied by means of the six electrical wires .78 to the spark plugs of the engine 74.

As may be seen in FIGURE 6, the voltage generator in FIGURE 5 comprises a circular hollow housing 80 which has a spider structure consisting of a central hollow core 82 with six radial walls 84 supporting the central core 82 and dividing the inside of the housing up into six separate chambers. Six pairs of piezoelectric cylinders respectively 86, 88 are supported in each chamber with the cylinder 88 having one end rigidly abutting the central core 82 and the cylinder 86 extending between the other end of the cylinder 88 and a piston 90. The abutting ends of the cylinders 86, 88 have a metal film thereon and connection is made externally therefrom to the leads 78 by means of a lead 92 connected to the film. The central rotating shaft 72 has a central opening 72A which connects to the pressurized fluid accumulator of the device. A radially extending passageway 72B in said shaft conducts the fluid in said central opening successively to the tubes 96, represented by dotted lines, which extend from adjacent the rotating shaft through the respective centers of the piezoelectric cylinders, to the region 98 which is behind the respective pistons 90. The pressure of the hydraulic fluid which is applied to the respective pistons is relieved by means of bleed off openings 1% which are made in the respective walls opposite the respective pistons 90. These bleed off openings extend through passageways, now shown, to a common collecting tube which then couples back to the fluid pump '76.

It is believed that the operation of the system should be fairly obvious. The shaft 72 rotates until the passageway 72B aligns itself with one of the tubes 96. The high pressure fluid in the accumulator can then be discharged into the space 98 behind one of the pistons The piston is moved to apply pressure to the piezoelectric cylinders thereby generating a high voltage. As the shaft continues to turn, the application of high pressure fluid to the specific piston is terminated and'the fluid pressure behind the piston is relieved via a bleed off opening 100 and the passageways provided therefor to return the fluid back to the fluid pump. The pressure on the piston is thus relieved. The shaft continues to turn and successively activates each one of the pistons in turn.

Another arrangement may be employed for the embodiment of the invention whereby instead of a high voltage being derived from the application of pressure to the piezoelectric cylinders, such voltage may be derived from the sudden removal of the pressure therefrom. A cross-sectional view of an arrangement for accomplishing this is shown in FIGURE 7. The housing contains a pressurized fluid accumulator cavity 114. A rotating shaft 116 driven by a motor (not shown) has a pump structure 118 at one end thereof. A low fluid pressure cavity 120 contains hydraulic fluid at a low pressure and a conduit 122 conducts this fluid to the pump 118. A second conduit 124 conducts the fluid to the pressurized fluid accumulator cavity 114. It will be appreciated that the cavity 114 may have structure consisting of a spring backed piston such as is shown in FIGURES 2 and 3.

The shaft 116 will have therein two valving passageways similar to the passageways 38, 40 which are shown in FIGURES 2 and 3. Only one of these passageways, the exit passageway 126, is shown in FIGURE 7. The entrance passageway, however, allows high pressure fluid from the accumulator 114 to be applied against the back side of a piston 128. A piston moves to compress two axially aligned piezoelectric cylinders respectively 130,. 132. The cylinder 132 has one end solidly abutted against a rubber shock pad 134, which in turn is held in place: against the inner wall of the housing 110. The other end. of the piezoelectric cylinder 132 has a metal deposit thereon and abuts a similarly finished end of the cylinder 130. A high voltage lead 136 connects to the abutting ends of the piezoelectric cylinders and extends to the outside of the high voltage generator surrounded by insulation 138. The lead 136 is connected through a high resistance bleeder resistor 140 to ground. The piston 128 compresses the piezoelectric'cylinders 130, 132 under the pressure of fluid from the high pressure reservoir 114.

Rubber reaction pads 142 are interposed between the piston 12S and the piezoelectric cylinder. Thus, these rubber reaction pads 1 42 together with the rubber'reaction pads 134 operate to cushion the sudden application of high pressure to the piezoelectric cylinders 13%), 132 by the piston 128. Also, the voltage which is generated as a result of the application of pressure to the cylinders is bled off through resistor 140.

As the shaft 116 continues to be turned, the passageway to the high pressure fluid reservoir is blocked, the piston remains in its pressure applying position however until the shaft is turned to couple the passageway 125 between the space behind the piston and a poppet valve 148. The pressure of the fluid behind the piston 142 exceeds the pressure required to open the poppet valve. The poppet valve 148 is normally closed to maintain the passage 126 blocked from another passage 150 leading to the low pressure fluid reservoir 129. The poppet valve is a high speed operating valve which may have an opening time on the order of 20 microseconds. The relatively large orifice created by the opened valve causes the fluid pressure at the back of the piston to drop quickly to approximately atmospheric level. As a result of the rapid fluid pressure drop, there is a rapid unloading of the pressure applied to the piezoelectric cylinders, as a result of which they generate a voltage pulse (of approximately 50 microsecond rise time) that is transmitted by the shielded conductor 136 to a spark plug.

At a predetermined reduced pressure, the poppet valve closes, sealing the hydraulic chamber for the next cycle. The fluid in the low pressure reservoir is pumped by the vane pump 118 back into the high pressure fluid accumulating chamber 114. The piezoelectric rods 13%, 132 are enclosed in an insulating boot 152, which may be made from one of several epoxy or elastomer compounds, such as silicon rubber, enabling a simple and inexpensive boot to be produced rapidly. A fluid vent 154 is provided as a release passage for any fluid which may leak past the plunger ring 156 which slidably seals the outside edge of the piston of the housing wall.

For a given engine r.p.m., the timing shaft subjects the poppet valve to the pressure behind the cylinder and which causes the valve to open at a particular crank angle, providing reproducible ignition timing, which is as accurate as that of the timing shaft with relation to the crank shaft. The ports in the shaft time the blow down process, and hence time the voltage generated by the ignition system. The function of the poppet valve is to govern the rate of the blow down process, and thus the voltage rise time produced by this system. As the engine r.p.m. increases, the fluid pressure in the chamber increases at a slower rate (due to fluid transfer), causing the poppet valve to open later, and the piezoelectric ceramic to be discharged later. Thus, timing retards with an increase in engine r.p.m. As a result of this retardation with increasing engine-r.p.m., and the requirement for spark advance with r.p.m., a greater degree of advance may be necessary for this ignition than for conventional systems. This advance is accomplished simply by rotating the housing 110 about the timing shaft, using the shaft bearing. Another feature of the ignition system in accordance with this invention is that the voltage generated by the piezoelectric ceramic remains constant with r.p.m., rather than decreasing with increase in r.p.m., as in conventional ignition systems. This constant voltage results from constant accumulator pressures; large area porting having high flow coefiicient, and low pressure drops and the constant pop olf pressure of the poppet valve.

An additional feature of this ignition system is that during engine start up, the spark voltage is substantially higher than in conventional ignition systems, because the Voltage generated by the piezoelectric system is independent of the engine r.p.rn. In conventional systems, the voltage is substantially lower at start up, especially with a cold battery subjected to the large power drain required for engine cranking.

FIGURE 8 is a cross-sectional view of another embodiment of this invention which does not utilize a rotating shaft as valve means. This embodiment of the invention is directly actuated by a cam (a portion of which is shown) which is on the cam shaft of the internal combustion engine with which the spark generator is employed. The high voltage generating equipment includes a housing block 162 which has a cylindrical opening drilled therein for holding the apparatus associated with the spark generator. This housing block is suitably mounted on or within the engine so that it may receive oil from the engines lubricating oil supply. This will become more clear as this description continues.

The cam drives a cam follower and plunger 164 which fills a portion of the opening in the housing 162. The cam follower and plunger can reciprocate within this opening, and has a slidable sealing ring 166, which can be made of Teflon, mounted on its periphery. The piston and plunger have a fluid relief passageway 168, which may take the form of a T, drilled therein. The openings at the ends of the bar of the T return the fluid, which is the engine lubricating oil, back to the engine lubricating oil supply source. The bottom of the T opens into a poppet valve 170, which functions to open and permit passage of fluid from a working region 172 through passageways 174 and 176, through the poppet valve 170 into the fluid relief passage 168, when the pressure of the fluid in the Working space 172 exceeds a predetermined value, as may be set in well known fashion with the poppet valve.

A movable piston 178 is spaced from the end of the cam follower and plunger 164. This piston is supported within the opening in the housing block by means of a leakproof sealing ring 180 whereby it may move sulficiently, in response to being actuated by a pressurized fluid, to bring pressure to bear upon two axially aligned piezoelectric cylinders 182, 184. The end of the piston 178 pushes against rubber pads 186 which transmit the pressure applied thereto to the piezoelectric cylinder 182. The end of the piezoelectric cylinder 184, which is adjacent the termination of the cavity within the housing block, abuts another set of rubber pads 188. Both of the sets of rubber pads 186 and 188 are respectively contained within L rings 190, 190 respectively.

The working space 172 is filled with engine oil from the lubricating oil supply of the engine, through a tube 194 which is connected to the working space through a valve 196. As the cam 160 lifts the integral cam follower plunger 164, there is an increase in the pressure on the fluid within the space 172 which forces the drive piston 178 upward, compressing the rubber reaction pads respectively 186 and 188 and the piezoelectric rods 182 and 184. The compression of these rods generates an electric charge which is gradually bled off through a bleeder resistor 198 which is connected to the lead 200, connected to the electrodes between the two piezoelectric rods. As the plunger continues to rise, the fluid pressure and the compressive loading on the piezoelectric rods increase.

At a predetermined fluid pressure, corresponding to a particular crank angle, the poppet valve 170 opens. This valve has a fast opening time (on the order of 20 microseconds) and a relatively large orifice created by the open valve, causes the fluid pressure in the working space 172 to drop quickly to the level (approximately atmospheric) of the fluid pressure in the relief passage 168. The time required for fluid pressure release is approximately 50 microseconds. This fluid pressure drop causes a rapid unloading of the piezoelectric rods, which in turn generate a voltage pulse that is transmitted by the shielded high voltage lead 200 to a spark plug. The rise time of the voltage pulse is approximately 50 microseconds. At a predetrrnined low pressure, the poppet valve closes, sealing the hydraulic chamber.

The integral cam follower plunger follows the negative ramp (closing flank of the cam 160) as the cam rotates past its flow point. This cam following action results from the downward reaction caused by the resilience of the 7 rubber reaction pads, housing and piezoelectric rods moving against the fluid in the chamber. As the plunger uncovers the fluid inlet orifice, the valve 196, which is a check valve, opens and fluid flows into the hydraulic chamber from the fluid supply line.

The elastic radial deformation of the metal L rings allows the captured rubber reaction pads to shear radially. This radial deformaiton occurs primarily toward the edge opposite to the surface which joins the rubber pad to the ceramic rod; however, the radial deformation of the ring at the sealing surface between the pad and the ceramic is negligible. This action gives resiliency (elastic compliance) to the piezoelectric drive mechanism, while preventing rubber extrusion past the ring and the ceramic. The slight radial expansion of the ceramic under compressive loading enhances this sealing action, further preventing rubber extrusion under high compressive loadings. In addition, these mounting pads allow for some degree of misalignment, surface mismatching, and inexact dimensional tolerances between the piezoelectric drive mechanism, the piezoelectric ceramic and the housing.

While the spark generator has been described as being utilized for the purpose of providing a voltage to a spark plug, it will be appreciated that this utility is exemplary only and should not be considered as restrictive. The device may have other uses, such as providing the voltage for a high voltage power supply or it can be used for charging capacitors, the output of which serves to provide the energy for driving subsequent equipment.

What is claimed is:

1. A high voltage generator comprising a piezoelectric body having opposite ends, means for substantially rigidly supporting one of said opposite ends of said body, piston means adjacent the other end for applying when actuated compressive pressure thereto, a source of fluid under a pressure required to actuate said piston means, valve means comprising a rotatable shaft first passageway, means throughsaid shaft for coupling said source of fluid under pressure to one of said piston means when said shaft has a first position, second passageway means through said shaft disposed in said shaft adjacent to said first passageway means for relieving the pressure of the fluid already applied to said piston means when said shaft has a second position which is at an angle relative to said first position, and means for deriving an electrical output from said piezoelectric body.

2. Apparatus as recited in claim 1 wherein there is included a poppet valve adjacent said second passageway for blocking said second passageway until the pressure of the fluid already applied to said piston means exceeds a predetermined amplitude.

3. A piezoelectric voltage generator comprising a piezoelectric body having opposite ends, means for rigidly supporting one of said opposite ends, piston means adjacent the other of said opposite ends for applying a compressive load to said piezoelectric body when actuated, a source of fluid under pressure, means for periodically applying fluid from said source to said piston means and for withdrawing said applied fluid from said piston means including a hydraulic fluid, means for accumulating said pressurized fluid coupled to said pump means, an entrance passageway between said means for accumulating pressurized fluid and said piston means for applying pressurized fluid from said means for accumulating pressurized fluid to said piston means, and valve means in said entrance and discharge passageways for admitting pressurized fluid from said means for accumulating to said piston means and for permitting the fluid applied to said piston means to be discharged through said discharge passage, and means for deriving an electrical output from said piezoelectric body.

4. Apparatus as recited in claim 3 wherein said valve means comprises a rotatably supported shaft, said shaft having a first passageway therethrough, and a second passageway through said shaft adjacent to and angularly disposed relative to said first passageway, said first passageway being aligned with said entrance passageway when said shaft has a first position, said second passageway being aligned with said discharge passageway when said shaft has a second position.

5. Apparatus as recited in claim 4 wherein said discharge passageway means include a poppet valve which blocks said passageway until the fluid pressure applied thereto exceeds a predetermined value.

6. A piezoelectric voltage generator comprising a piezoelectric body having opposite ends, means for rigidly supporting one of said opposite ends, movable piston means adjacent to the other of said opposite ends for applying comprcssive pressure to said piezoelectric voltage generator, means for alternately applying and relieving pressure on said piston means, and means for deriving an electrical output from said ceramic body; said means for applying and relieving hydraulic pressure on said piston means including a chamber, a piston movably mounted within said chamber, resilient means at one end of said chamber for biasing said piston toward the other end of said chamber, a source of hydraulic fluid under pressure, inlet passage means coupling said source of hydraulic fluid under pressure to said other end of said chamber, outlet passage means for enabling the application of said fluid under pressure in said other end of said chamber to said piston means, and valve means for alternately opening said outlet passage means and for blocking said outlet passage means and relieving the fluid pressure on said piston means.

7. Apparatus as recited in claim 6 wherein said valve means comprises a rotatable shaft, said rotatable shaft having a first slot therethrough for completion ofthe outlet passage means between said one end of said chamber and said piston, and a second slot therethrough displaced from said first slot for relieving the pressure of said hydraulic fluid on said piston means.

8. Apparatus as recited in claim 6 wherein said shaft means includes a pump at one end thereof for pressurizing said hydraulic fluid.

9. A high voltage generator comprising first and second cylinders made of piezoelectric material, means axially aligning said first and second cylinders, an electrode between said first and second cylinders, support means for solidly supporting one end of said aligned first and second cylinders, a piston positioned adjacent to the other end of said aligned cylinders for applying compressive pressures thereto, means for applying and relieving pressure on said piston comprising a source of fluid under pressure, a relatively low pressure reservoir, rotary valve means for alternately coupling said source of fluid under pressure to said piston and for blocking the application of said fluid under pressure to said piston while enabling the fluid applied to said piston previously to escape to said low pressure reservoir, poppet valve means between said low pressure reservoir and said rotary valve means for blocking passage of fluid from said rotary valve means to said low pressure reservoir until the pressure of said fluid exceeds a predetermined value, and means for deriving an electrical output from said first and second cylinders.

10. Apparatus as recited in claim 9 wherein said source of hydraulic fluid under pressure comprises a chamber having a piston slidably supported therein, spring means for biasing said piston toward one end of said chamber, pump means for pumping hydraulic fluid under pressure to said one end of said chamber, and exit passage means coupling said one end of said chamber to said rotary valve means.

11. A piezoelectric high voltage generator comprising a plurality of piezoelectric cylinders, a central body, said plurality of cylinders arranged to extend radially outward with one of their ends resting on said central 'body,

a piston means for each of said plurality of cylinders, each 9 said piston means being positioned adjacent the other of the ends of each of said piezoelectric cylinders for applying compressive forces thereto when actuated, means 7 for successively actuating each of said piezoelectric cylinders comprising a source of fluid under 'high pressure, means for successively applying fluid from said source to each of said piston means, means for relieving the fluid pressure applied to each of said piston means, and means for deriving an electrical output from each of said piezoelectric cylinders.

12. A piezoelectric high voltage generator as recited in claim 11, wherein said means for successively applying fluid from said source to each of said piston means includes a rotary shaft rotatably mounted in said central body, a separate passageway extending from each of said piston means to said rotary shaft, and an input passageway in said shaft extending between said source of fluid under pressure and each of said separate passageways as said shaft is rotated.

13. A piezoelectric high voltage generator comprising a piezoelectric body having opposite ends, means for substantially rigidly supporting one of said opposite ends of said body, piston means adjacent the other end of said body for applying when actuated compressive pressures to said other of said opposite ends, means defining a fluid chamber, said means including the side of said piston means Which is opposite the side adjacent said piezoelectric body, said means further including a cam actuated plunger forming a wall of said fluid chamber opposite to the Wall formed by said piston means, a fluid escape passage in said cam actuated plunger communicating with said fluid chamber, valve means in said fluid escape passage for blocking said passage for the escape of fluid until said fluid exceeds a predetermined pressure, a source of fluid supply coupled to said fluid chamber, cam means for moving said cam actuated plunger toward said piston means for applying pressure to said fluid in said chamber and thereby to said piston means and said piezoelectric body, and means for deriving an electrical output from said piezoelectric body.

14. A high voltage generator comprising a cylinder of piezoelectric material, means for substantially solidly supporting one end of said cylinder, piston means adjacent the other end of said cylinder for applying when actuated compressive pressure to said piezoelectric cylinder, and means for hydraulically actuating said piston means comprising cam actuated means for applying fluid under pressure to said piston means, and means Within said cam actuated means for rapidly relieving the fluid pressure applied to said piston means.

15. Apparatus as recited in claim 14 wherein said cam operated cam follower means comprises a cam operated plunger having a fluid release passageway therein, a poppet valve in said fluid release passage for blocking said passage until such time as the pressure or fluid applied thereto exceeds a predetermined value.

16. A voltage generator for an internal combustion engine comprising a piezoelectric cylinder, means for supporting one end of said piezoelectric cylinder substantially rigidly, a piston means, means for supporting said piston means adjacent the other end of said piezoelectric cylinder for applying compressive pressure thereto when actuated, means for hydraulically actuating said piston means driven by said internal combustion engine, said means including a source of liquid, means for applying liquid from said source under pressure to said piston means to cause it to be actuated, means for relieving the pressure of said liquid on said piston means, means for deriving a high voltage from said piezoelectric cylinder, and means for applying said voltage to said internal combustion engine.

References Cited UNITED STATES PATENTS 3,217,163 11/1965 Gogan. 3,215,133 11/1965 Farrell. 3,166,684 1/ 1965 Williams.

MILTON O. HI-RSHFIELD, Primary Examiner. J. D. MILLER, Examiner. 

1. A HIGH VOLTAGE GENERATOR COMPRISING A PIEZELECTRIC BODY HAVING OPPOSITE ENDS, MEANS FOR SUBSTANTIALLY RIGIDLY SUPPORTING ONE OF SAID OPPOSITE ENDS OF SAID BODY, PISTON MEANS ADJACENT THE OTHER END FOR APPLYING WHEN ACTUATED COMPRESSIVE PRESSURE THERETO, A SOURCE OF FLUID UNDER A PRESSURE REQUIRED TO ACTUATED SAID PISTON MEANS, VALVE MEANS COMPRISING A ROTATABLE SHAFT FIRST PASSAGEWAY, MEANS THROUGH SAID SHIFT FOR COUPLING SAID SOURCE OF FLUID UNDER PRESSURE TO ONE OF SAID PISTON MEANS WHEN SAID SHAFT HAS A FIRST POSITION, SECOND PASSAGEWAY MEANS THROUGH SAID SHAFT DISPOSED IN SAID SHAFT ADJACENT TO SAID FIRST PASSAGEWAY MEANS FOR RELIEVING THE PRESSURE OF THE FLUID ALREADY APPLIED TO SAID PISTON MEANS WHEN SAID SHAFT HAS A SECOND POSITION WHICH IS AT AN ANGLE RELATIVE TO SAID FIRST POSITION, AND MEANS FOR DERIVING AN ELECTRICAL OUTPUT FROM SAID PIEZOELECTRIC BODY. 